The WO 2008/044214 A1 discloses a biosensor for the detection of target components in a sample fluid. Magnetic particles are provided as dry reagents in a layer on top of a surface with capture antibodies. When the sample fluid is added, the magnetic particles are rapidly solved and distributed within the whole fluid such that binding sites on the magnetic particles can bind to target components of the sample. The magnetic particles are then attracted by magnetic forces to the capture antibodies, where further binding takes place. Target components bound to the surface are then detected for instance by frustrated total internal reflection (FTIR).
When a sample fluid like whole blood is processed, the target components are often substances of blood plasma while the blood cells are particles which disturb the detection process. Accordingly, samples like blood usually have to be filtered before detection in order to remove disturbing particles.